There is conventionally known a portable work tool such as an impact driver for fastening a screw. Such a portable work tool includes a housing (outer frame) whose outer surface is partially covered with a layer made from a soft material. The portable work tool also includes a drive source such as a motor, a transmission mechanism configured to transmit a drive force generated by the drive source to an end bit, and a trigger switch configured to control the drive source, i.e., to start and stop the drive source. The housing includes a main body housing that accommodates the drive source and the transmission mechanism therein, and a handle housing that extends from the main body housing and accommodates the trigger switch therein.
As an example of such a conventional portable work tool, an impact driver 101 will be described while referring to FIGS. 13 and 14. In the following description, the left side in FIG. 13 will be defined as the front side, while the right side in FIG. 13 will be defined as the rear side. The top and bottom sides in FIG. 13 will be defined as the top and bottom sides, respectively. The left and right sides of the impact driver 101 will be based on the perspective of a user facing the rear side of the impact driver 101.
As shown in FIG. 13, the impact driver 101 includes a housing 102 serving as an outer frame thereof and defining an outer shape thereof, and a hammer casing 103 (FIG. 14). The housing 102 includes a main body housing 102A and a handle housing 102B. The main body housing 102A is formed substantially in a cylindrical shape, extending in a front-rear direction. The handle housing 102B continuously extends downward from the main body housing 102A, being formed substantially in a T-shape in a side view. As shown in FIG. 14, inside the main body housing 102A, the impact driver 101 includes a motor 104, a planetary gear mechanism 105, and an impact mechanism 106 are accommodated. The motor 104 serves as a drive source. The planetary gear mechanism 105 is adapted to decelerate rotation of the motor 104. The impact mechanism 106 is adapted to convert the rotation of the motor 104 decelerated by the planetary gear mechanism 105 into a rotational impact force to transmit the rotational impact force to an end bit (not illustrated).
A trigger switch 110 and a battery pack receiving portion 108 are provided at the handle housing 102B. The trigger switch 110 is disposed at an upper portion of the handle housing 102B and adapted to control the motor 104 to start and stop rotation of the motor 104. The battery pack receiving portion 108 is disposed at a lower portion of the handle housing 102B. A rechargeable battery pack 109 as a power source is detachably mounted at the battery pack receiving portion 108.
Outer surfaces of the main body housing 102A and the handle housing 102B of the housing 102 are partially covered with a soft layer 112 made from a soft elastic material, such as elastomer. A shaded portion in FIG. 13 represents a portion where the soft layer 112 covers the outer surface of the housing 102. The soft layer 112 is provided for the purpose of, for example, improving operability of the impact driver 101 while a user operates the impact driver 101 and protecting the impact driver 101 from external shock.